The invention relates to a pipe which is provided with an external foam plastic layer carrying a covering outer layer and a process of manufacturing same.
Pipes with a foam plastic insulation, mostly consisting of a metal pipe carrying a foam plastic layer on the outer surface and a covering outer layer are known. This covering layer may consist of thermoplastic material or thermosetting material. Such tubes present the disadvantage that the covering layer is not perfectly water tight and gas tight. An example of a covering layer which is not gas and water tight under extreme conditions such as on the bottom of a river, is a covering layer obtained by wrapping thermoplastic tape material helically or non-helically round the foam plastic layer whereby the overlapping portions of the tape are connected by glueing.
As the pipes are at present applied on a large scale for the transport of fluids of low temperature, e.g. liquefied hydrocarbons, over long distances absolutely reliable gas and water tight covering outer layers and connections are required. This holds the more so as loss of insulation might give rise to accidents by a sudden evaporation of the liquid gas.